Coupled use of Fe-impregnated biochar and urea-hydrogen peroxide to simultaneously reduce soil-air emissions of fumigant and improve crop growth.

Reducing the emissions of soil fumigants such as 1,3-dichloropropene (1,3-D) is essential to protecting air quality. Although biochar is useful in reducing such emissions, biochar-adsorbed fumigants may desorb and cause secondary air pollution. This study investigated the degradation of 1,3-D on iron (Fe)-impregnated biochar (FBC) amended with urea-hydrogen peroxide (UHP). The results indicated the degradation rate of trans-1,3-D on FBC-UHP was 54-fold higher than that on pristine biochar (PBC). Electron paramagnetic resonance (EPR) combined with other characterization methods revealed that the presence of semiquinone-type radicals in FBC effectively accelerated the Fe(III)/Fe(II) cycleto maintain enough Fe(IIII) for UHP activation and ·OH generation. ·OH, rather than ·O2-, was the dominant active oxidant. Soil column tests showed that application of FBC to the soil surface reduced cumulative 1,3-D emissions from 34.80 % (bare soil) to 0.81%. After the column experiment, the mixing of the FBC with UHP resulted in the residual cis-isomers decreasing from 32.5% to 10.5%. Greenhouse bioassays showed that mixing post-1,3-D degradation FBC-UHP with soil significantly promoted lettuce growth relative to PBC. The findings of this study provide a new approach for biochar application, especially for the emission reduction of hazardous volatile organic compounds from soil.